Wednesday, March 7

Publish Events For User Control In Asp.Net Using Deligates


// In your user control
public delegate void evtSomething(SomeData oYourData);
public event evtSomething OnSomething;
// In the page using your user control
ucYourUserControl.OnSomething += ucYourUserControl_OnSomething;
// Then implement the function
protected void ucYourUserControl_OnSelect(SomeData oYourData)
{
   ...
}

If You wants to know what is deligate then take a small example:-

So what is delegate?
Basically it is similar like the old "C" age function pointer, where functions can be assigned like a variable and called in the run time based on dynamic conditions. C# delegate is the smarter version of function pointer which helps software architects a lot, specially while utilizing design patterns.
At first, a delegate is defined with a specific signature (return type, parameter type and order etc). To invoke a delegate object, one or more methods are required with the EXACT same signature. A delegate object is first created similar like a class object created. The delegate object will basically hold a reference of a function. The function will then can be called via the delegate object.
Sounds easy? If not lets have a look in the code snippets below.
 1. Defining the delegate
 
public delegate int Calculate (int value1, int value2);
 2. Creating methods which will be assigned to delegate object
 
//a method, that will be assigned to delegate objects
//having the EXACT signature of the delegatepublic int add(int value1, int value2)
{
    return value1 + value2;            
}
//a method, that will be assigned to delegate objects
//having the EXACT signature of the delegatepublic int sub( int value1, int value2)
{
    return value1 - value2;            
}
 3. Creating the delegate object and assigning methods to those delegate objects
 
//creating the class which contains the methods 
//that will be assigned to delegate objectsMyClass mc = new MyClass();

//creating delegate objects and assigning appropriate methods
//having the EXACT signature of the delegateCalculate add = new Calculate(mc.add);
Calculate sub = new Calculate(mc.sub);
 4. Calling the methods via delegate objects
 
//using the delegate objects to call the assigned methods Console.WriteLine("Adding two values: " + add(10, 6));
Console.WriteLine("Subtracting two values: " + sub(10,4));
Pretty simple,  Happy coding!!
Download source code.
Thanks Shibashish Mohanty

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